Method and apparatus for failure processing procedure in side link relay system

Abstract

To provide a failure processing procedure in a side link relay system.SOLUTION: There are provided a method and an apparatus for a failure processing procedure in a side link relay system under a third generation partnership project (3GPP) 5G new radio (NR). The method can include the steps of: establishing PC5 radio resource control (RRC) connection of a link between user equipment (UE) and a relay UE, in which PC5 RRC connection of a link between the relay UE and a separate UE is established; receiving a failure notification from the relay UE, in which the failure notification indicates occurrence of a failure on the ink between the relay UE and the separate UE; monitoring a discovery resource pool in response to reception of the failure notification from the relay UE; and reporting the failure information associated with the relay connection, to a base station (BS).SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] Embodiments of the present application generally relate to wireless communication technologies, and more particularly to methods and apparatuses for fault handling procedures in a sidelink relay system.

Background Art

[0002] Vehicle to Everything (V2X) has been introduced into 5G wireless communication technology. From the perspective of the channel structure of V2X communication, the direct link between two user equipments (UEs) is called a sidelink. The sidelink is a Long Term Evolution (LTE) function introduced in 3GPP (registered trademark) Release 12, which enables direct communication between neighboring UEs, and data does not need to go through a base station (BS) or a core network.

[0003] In the Third Generation Partnership Project (3GPP), the deployment of relay nodes (RNs) in a wireless communication system is promoted. One purpose of deploying an RN is to enhance the coverage area of a BS by improving the throughput of user equipments (UEs) located within the coverage or far from the BS, which may result in relatively low signal quality. An RN may also be named a relay UE in some cases. A 3GPP 5G sidelink system including a relay UE may be named a sidelink relay system.

[0004] Currently, in 3GPP 5G New Radio (NR) systems and the like, details regarding how to provide fault handling procedures in a sidelink relay system have not yet been specifically discussed.

Summary of the Invention

Means for Solving the Problems

[0005] Some embodiments of the present application provide a method for wireless communication. The method may be performed by a UE. The method includes establishing a PC5 Radio Resource Control (RRC) connection for a link between the UE and a relay UE, where a PC5 RRC connection for a link between the relay UE and another UE has been established, and receiving a failure notification from the relay UE, where the failure notification indicates the occurrence of a failure on a link between the relay UE and the above-mentioned another UE.

[0006] Some embodiments of the present application also provide an apparatus for wireless communication. The apparatus includes a non-transitory computer-readable medium storing computer-executable instructions, a receiving circuitry, a transmitting circuitry, and a processor coupled to the non-transitory computer-readable medium, the receiving circuitry, and the transmitting circuitry, where the computer-executable instructions cause the processor to implement the above-mentioned method for receiving a failure notification performed by a UE.

[0007] Some embodiments of the present application provide a further method for wireless communication. The method may be performed by a relay UE. The method includes detecting whether a failure has occurred on a link between the relay UE and another UE, where a PC5 RRC connection for a link between the UE and the relay UE has been established and a PC5 RRC connection for a link between the relay UE and the above-mentioned another UE has been established, and transmitting a failure notification to the UE in response to detecting that a failure has occurred on a link between the relay UE and the above-mentioned another UE, where the failure notification indicates the occurrence of a failure on a link between the relay UE and the above-mentioned another UE.

[0008] Some embodiments of the present application also provide an apparatus for wireless communication. The apparatus includes a non-transitory computer-readable medium storing computer-executable instructions, a receiving network, a transmitting network, and a processor coupled to the non-transitory computer-readable medium, the receiving network, and the transmitting network, and the computer-executable instructions cause the processor to implement the above-described further method for transmitting a failure notification performed by a relay UE.

[0009] Some embodiments of the present application also provide a further method for wireless communication. The method may be performed by a UE. The method includes transmitting, by the UE, an RRC reconfiguration message for a relay side link to a relay UE, wherein an RRC relay connection of a link between the UE and another UE is established; starting a timer for controlling a reconfiguration procedure; and reporting failure information to a BS in response to expiration of the timer or in response to receiving an RRC reconfiguration failure message for the relay side link from the relay UE, wherein the failure information indicates a failure on the RRC relay connection of the link between the UE and the above-mentioned another UE.

[0010] Some embodiments of the present application also provide an apparatus for wireless communication. The apparatus includes a non-transitory computer-readable medium storing computer-executable instructions, a receiving network, a transmitting network, and a processor coupled to the non-transitory computer-readable medium, the receiving network, and the transmitting network, and the computer-executable instructions cause the processor to implement the above-described further method for reporting failure information performed by a UE.

[0011] Some embodiments of the present application also provide a further method for wireless communication. The method may be performed by a relay UE. The method includes receiving, by the relay UE, an RRC reconfiguration message for a relay side link from a UE; starting a timer for controlling a reconfiguration procedure; and transmitting, in response to receiving an RRC reconfiguration failure side link message from another UE, an RRC reconfiguration failure message for the relay side link to the UE.

[0012] Some embodiments of the present application also provide an apparatus for wireless communication. The apparatus includes a non-transitory computer-readable medium storing computer-executable instructions, a receiving network, a transmitting network, and a processor coupled to the non-transitory computer-readable medium, the receiving network, and the transmitting network, and the computer-executable instructions cause the processor to implement the above-described further method for transmitting an RRC reconfiguration failure message for a relay sidelink performed by a relay UE.

[0013] The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.

[0014] To describe the manner in which the advantages and features of the present application can be obtained, the description of the present application has been made by referring to specific embodiments thereof illustrated in the accompanying drawings. These drawings depict only exemplary embodiments of the present application and are therefore not to be considered as limiting its scope. BRIEF DESCRIPTION OF THE DRAWINGS

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

DETAILED DESCRIPTION OF THE INVENTION

[0016] The detailed description of the accompanying drawings is intended as a description of the preferred embodiments of the present application and is not intended to represent the only form in which the present application can be implemented. It should be understood that the same or equivalent functions can be achieved by various embodiments intended to be included within the spirit and scope of the present application.

[0017] Here, some embodiments of the present application will be referred to in detail, and examples thereof are illustrated in the accompanying drawings. For ease of understanding, the embodiments are provided under specific network architectures and new service scenarios such as 3GPP 5G, 3GPP LTE Release 8, etc. It is contemplated that all embodiments in the present application are applicable to the same technical problems with the development of network architectures and new service scenarios. Moreover, although the technical terms listed in the present application may change, they should not affect the principles of the present application.

[0018] FIG. 1 illustrates an overview of a wireless communication system according to some embodiments of the present application.

[0019] As illustrated in FIG. 1, the wireless communication system 100 includes, for illustrative purposes, two UEs (i.e., UE101a and UE101b), BS102, and relay UE103. Although a specific number of UEs, relay UEs, and BSs are depicted in FIG. 1, it is contemplated that any number of UEs, relay UEs, and BSs may be included in the wireless communication system 100.

[0020] Due to the long distance between UE101a and UE101b, these two UEs communicate with each other via relay UE103. UE101a and UE101b may be connected to relay UE103 via a network interface, for example, a PC5 interface as defined in 3GPP standard documents. UE101a may be connected to BS102 via a network interface, for example, a Uu interface as defined in 3GPP standard documents. Referring to FIG. 1, UE101a is connected to relay UE103 via PC5 link 1, UE101b is connected to relay UE103 via PC5 link 2, and UE101a is connected to BS102 via a Uu link.

[0021] In some embodiments of the present application, UE101a, UE101b or relay UE103 may include a computing device such as a desktop computer, a laptop computer, a personal digital assistant (PDA), a tablet computer, a smart TV (e.g., a TV connected to the Internet), a set-top box, a game console, a security system (including a security camera), a vehicle-mounted computer, a network device (e.g., a router, a switch, and a modem), etc.

[0022] In some further embodiments of the present application, UE101a, UE101b or relay UE103 may include a portable wireless communication device, a smartphone, a cellular phone, a foldable phone, a device with a subscriber identity module, a personal computer, a selective call receiving circuit network, or any other device capable of transmitting and receiving communication signals on a wireless network.

[0023] In some other embodiments of the present application, UE101a, UE101b, or relay UE103 may include wearable devices such as smartwatches, fitness bands, optical head-mounted displays, etc. Moreover, UE101a, UE101b, or relay UE103 may be referred to as a subscriber unit, mobile, mobile station, user, terminal, mobile terminal, wireless terminal, fixed terminal, subscriber station, user terminal or device, or may be described using other technical terms used in the art.

[0024] BS102 may be distributed over a geographical area. In some embodiments of the present application, each of BS102 may be referred to as an access point, access terminal, base, base unit, macrocell, Node B, evolved Node B (eNB), gNB, home Node B, relay node or device, or may be described using other technical terms used in the art. BS102 is generally part of a wireless access network that may include one or more controllers communicatively coupled to one or more corresponding BS102.

[0025] Wireless communication system 100 may be compatible with any type of network capable of transmitting and receiving wireless communication signals. For example, wireless communication system 100 may be compatible with a wireless communication network, a cellular telephone network, a time division multiple access (TDMA)-based network, a code division multiple access (CDMA)-based network, an orthogonal frequency division multiple access (OFDMA)-based network, an LTE network, a 3GPP-based network, a 3GPP 5G network, a satellite communication network, a high altitude platform network, and / or other communication networks.

[0026] In some embodiments of the present application, the wireless communication system 100 is compatible with 5G NR of the 3GPP protocol. BS102 transmits data using the OFDM modulation scheme on the downlink (DL), and UE101 (e.g., UE101a, UE101b, or other similar UEs) transmits data on the uplink (UL) using the discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S-OFDM) or cyclic prefix OFDM (CP-OFDM) scheme. However, more generally, the wireless communication system 100 may implement some other open or proprietary communication protocols, such as WiMAX, among other protocols.

[0027] In some embodiments of the present application, BS102 may communicate using other communication protocols, such as the wireless communication protocol of the IEEE802.11 family. Further, in some embodiments of the present application, BS102 may communicate through licensed spectrum, while in other embodiments, BS102 may communicate through unlicensed spectrum. The present application is not intended to be limited to any particular wireless communication system architecture or protocol implementation. In still some other embodiments of the present application, BS102 may communicate with UE101 using the 3GPP 5G protocol.

[0028] UE101 may access BS102 to receive data packets from BS102 via the downlink channel and / or transmit data packets to BS102 via the uplink channel. In normal operation, since UE101 does not know when BS102 will transmit data packets to UE101, UE101 is constantly active and must monitor the downlink channel (e.g., the Physical Downlink Control Channel (PDCCH)) to be ready to receive data packets from BS102. However, if UE101 continuously monitors the downlink channel even when there is no traffic between BS102 and UE101, it will result in significant power waste, which is a problem for UEs with limited power or power-sensitive UEs.

[0029] Figure 2 illustrates an exemplary flowchart of a sidelink RRC reconfiguration procedure according to some embodiments of the present application.

[0030] As illustrated in Figure 2, at step 201, UE (a) (e.g., UE101a or UE101b as illustrated and exemplified in Figure 1) starts the sidelink RRC reconfiguration procedure for UE (b) by transmitting an RRCReconfigurationSidelink message to UE (b) (e.g., UE101b or UE101a as illustrated and exemplified in Figure 1).

[0031] If the sidelink RRC reconfiguration procedure is successfully completed, at step 202, UE (b) may transmit an "RRC reconfiguration complete sidelink message", e.g., an RRCReconfigurationCompleteSidelink message as defined in the 3GPP standard document, to UE (a). Alternatively, if the sidelink RRC reconfiguration procedure is not successfully completed, at step 202, UE (b) may transmit an "RRC reconfiguration failure sidelink message", e.g., an RRCReconfigurationFailureSidelink message as defined in the 3GPP standard document, to UE (a).

[0032] The purpose of the sidelink RRC reconfiguration procedure is to change the PC5 RRC connection, for example, to establish, modify, or release a sidelink data radio bearer (DRB), to configure NR sidelink measurements and reporting, and to configure sidelink channel state information (CSI) reference signal resources.

[0033] A UE (e.g., UE (a) as illustrated and shown in FIG. 2) may initiate the sidelink RRC reconfiguration procedure and operate on the PC5 RRC connection corresponding to the following cases: - Release of a sidelink DRB associated with a peer UE (e.g., UE (b) as illustrated and shown in FIG. 2), - Establishment of a sidelink DRB associated with a peer UE, - Changes to the parameters included in the sidelink radio bearer (SLRB)-Config of a sidelink DRB associated with a peer UE, - Configuration information of a peer UE for performing NR sidelink measurements and reporting, and - Configuration information of sidelink CSI reference signal resources.

[0034] A UE capable of NR sidelink communication may initiate the procedure for sidelink UE information for NR in order to report to the network or BS that a sidelink radio link failure (RLF) (e.g., expiration of timer T400) or a sidelink RRC reconfiguration failure has been declared.

[0035] The following table shows the introduction of timer T400 as defined in 3GPP specification documents, including the start condition, stop condition, actions upon expiration, and possible general names for the timer.

[0036]

Table 1

[0037] FIG. 3 illustrates an exemplary flowchart of the sidelink UE information procedure according to some embodiments of the present application.

[0038] As shown in FIG. 3, in step 301, a UE (e.g., UE101a or UE101b as illustrated and shown in FIG. 1 or UE(a) as illustrated and shown in FIG. 2) sends a "Sidelink UE Information NR Message", e.g., a SidelinkUEinformationNR message as defined in 3GPP standard documents, to a BS (e.g., BS102 as illustrated and shown in FIG. 1). Specifically, the sidelinkUEinformationNR message may include sidelink failure information. The sidelink failure information may include sidelink destination identification information (ID) and the cause of sidelink failure.

[0039] Currently, in the sidelink relay system under 3GPP 5G NR, details regarding how to provide a failure handling procedure have not yet been specifically discussed. Embodiments of the present application provide a failure handling procedure in a sidelink relay system, e.g., whether a relay UE reports a failure notification to a UE when an RLF of a link between the relay UE and another UE occurs or when the relay UE receives an RRCReconfigurationFailureSidelink message from another UE. Further details will be illustrated in the following text in combination with the accompanying drawings.

[0040] FIG. 4 illustrates a flowchart of a method for receiving a failure notification according to some embodiments of the present application. This method may be performed by a UE (e.g., UE101a or UE101b as illustrated and shown in FIG. 1, UE(a) as illustrated and shown in FIG. 2, or UE as illustrated and shown in FIG. 3). Although described with respect to a UE, it should be understood that other devices may be configured to perform a method similar to that of FIG. 4.

[0041] In an exemplary method 400 as illustrated in FIG. 4, at operation 401, a UE (e.g., UE 101a illustrated and shown in FIG. 1) establishes a PC5 RRC connection of a link between the UE and a relay UE (e.g., relay UE 103 illustrated and shown in FIG. 1). The embodiment of FIG. 4 assumes that a PC5 RRC connection of a link between the relay UE and another UE (e.g., UE 101b illustrated and shown in FIG. 1) has been established.

[0042] In one example, the UE further establishes an RRC relay connection of a link between the UE and the other UE as described above. The RRC relay connection of the link is a logical link and may also be named an "end-to-end link" between the UE and the other UE as described above.

[0043] At operation 402, the UE receives a failure notification from the relay UE. The failure notification indicates the occurrence of a failure on the link between the relay UE and the other UE as described above. The failure notification may be included in RRC signaling, a control packet data unit (PDU) in the sidelink adaptation protocol (SLAP) layer, and a MAC control element (CE).

[0044] In one embodiment, the failure notification includes the ID of the other UE as described above, which may also be named a destination ID. For example, referring to FIG. 1, the failure notification ● If an end-to-end link between UE 101a and UE 101b is established, the destination ID associated with the end-to-end link, or ● Includes the destination ID associated with the link between relay UE 103 and UE 101b.

[0045] In a further embodiment, the failure notification includes a failure cause. The failure cause can be a "sidelink radio link failure (RLF)" or a "configuration failure". For example, RLF is included in the failure notification for sidelink RLF, and the configuration failure is included in the failure notification for sidelink RRC reconfiguration failure. The failure notification ● Reached the maximum number of retransmissions of the RLC entity of the relay UE, ● Expiration of a timer (e.g., timer T400) for transmitting RRC reconfiguration for sidelink, ● Reaching the maximum number of consecutive hybrid automatic repeat request (HARQ) discontinuous transmission (DTX), and ● May further include at least one failure cause of integrity check failure.

[0046] According to some embodiments, the UE further declares a sidelink radio link failure (RLF) of the link between the UE and the relay UE. If an RRC relay connection of the link between the UE and another UE as described above is established, the UE may further declare a sidelink RLF of the link between the UE and another UE as described above.

[0047] According to some embodiments, the UE further releases the data radio bearer (DRB) and signaling radio bearer (SRB) of the link between the UE and the relay UE, and discards the sidelink communication configuration information of the link between the UE and the relay UE. If an RRC relay connection of the link between the UE and another UE as described above is established, the UE may further release the DRB and SRB of the link between the UE and another UE as described above, and the UE may further discard the sidelink communication configuration information of the link between the UE and another UE as described above.

[0048] According to some embodiments, the UE further ● Resets the sidelink-specific media access control (MAC) configuration information of the link between the UE and the relay UE, ● Sets the connection state of the link between the UE and the relay UE to a released state, and ● Indicates the "released state of the link between the UE and the relay UE" to the upper layer of another UE as described above.

[0049] If an RRC relay connection of the link between the UE and another UE as described above is established, the UE further ● Resets the sidelink-specific MAC configuration information of the link between the UE and another UE as described above, ● Sets the connection state of the link between the UE and another UE as described above to a released state, and ● The upper layer of the other UE described above may indicate the release state of the link between the UE and the other UE described above.

[0050] According to some embodiments, the UE further determines whether it is within the coverage of a BS (e.g., the BS 102 illustrated and shown in FIG. 1). If the UE determines that it is within the coverage of the BS, the UE may report fault information to the BS in response to receiving a fault notification. The fault information is associated with the received fault notification.

[0051] For example, the fault information may include the state of the link between the UE and the relay UE, and the state of the link between the relay UE and the other UE described above. The state of the link between the UE and the relay UE may represent "occurrence of RLF" or "the link is available". Similarly, the state of the link between the relay UE and the other UE described above may represent "occurrence of RLF" or "the link is available".

[0052] According to some embodiments, the UE further receives an RRC reconfiguration message from the BS and performs a relay reselection procedure. The RRC reconfiguration message instructs the UE to perform a relay reselection procedure. According to some other embodiments, the UE performs a relay reselection procedure in response to receiving a fault notification.

[0053] During the relay reselection procedure, the UE monitors a discovery resource pool to find one or more relay UEs and selects one relay UE from the one or more found relay UEs. The UE may further establish a PC5 RRC connection for the link between the UE and the selected relay UE.

[0054] All the details described in all other embodiments of this application (e.g., details of how to handle faults on the link between the relay UE and the UE) are applicable to the embodiment of FIG. 4. Moreover, the details described in the embodiment of FIG. 4 are applicable to all embodiments of FIGS. 1 - 3 and FIGS. 5 - 8.

[0055] FIG. 5 illustrates a flowchart of a method for transmitting a failure notification according to some embodiments of the present application. This method may be performed by a relay UE (e.g., relay UE 103 illustrated and shown in FIG. 1). Although described with respect to a UE, it should be understood that other devices may be configured to perform a method similar to that of FIG. 5.

[0056] In an exemplary method 500 as illustrated in FIG. 5, a PC5 RRC connection of a link between a UE (e.g., UE 101a illustrated and shown in FIG. 1) and a relay UE (e.g., relay UE 103 illustrated and shown in FIG. 1) is established, and a PC5 RRC connection of a link between the relay UE and another UE (e.g., UE 101b illustrated and shown in FIG. 1) is established. In operation 501, the relay UE detects whether a failure has occurred on the link between the relay UE and the other UE described above. In operation 502, if the relay UE detects that a failure has occurred on the link between the relay UE and the other UE described above, the relay UE transmits a failure notification to the UE to indicate the occurrence of the failure on the link between the relay UE and the other UE described above.

[0057] In one example, the failure is a sidelink RLF of the link between the relay UE and the other UE described above. In a further example, the failure is a failure during an RRC reconfiguration procedure between the relay UE and the other UE described above, and the failure notification is an "RRC reconfiguration failure message for relay sidelink".

[0058] The failure notification in the embodiment of FIG. 5 may be in a similar format or content to those of the failure notification in the embodiment of FIG. 4. For example, similar to the embodiment of FIG. 4, in the embodiment of FIG. 5, the failure notification includes a cause of the failure, such as a sidelink RLF or a configuration failure.

[0059] According to some embodiments, the failure notification in the embodiment of FIG. 5 includes the ID of another UE described above, which may also be named the destination ID. For example, referring to FIG. 1, the failure notification includes the destination ID associated with the link between relay UE 103 and UE 101b, or the destination ID associated with the end-to-end link if the end-to-end link between UE 101a and UE 101b is established.

[0060] All the details described in all other embodiments of this application (for example, details of how to handle a failure on the link between a relay UE and a UE) are applicable to the embodiment of FIG. 5. Moreover, the details described in the embodiment of FIG. 5 are applicable to all embodiments of FIGS. 1-4 and FIGS. 6-8.

[0061] The following text describes specific embodiments 1 and 2 of the method as illustrated and exemplified in FIGS. 4 and 5.

[0062] Embodiment 1 According to Embodiment 1, a UE (for example, UE 101a as illustrated and exemplified in FIG. 1), a relay UE (for example, relay UE 103 as exemplified and illustrated in FIG. 1), and another UE (for example, UE 101b as illustrated and exemplified in FIG. 1) perform the following steps: (1) The PC5 RRC connection of PC5 link 1 between UE 101a and relay UE 103 is established. Another PC5 RRC connection of PC5 link 2 between relay UE 103 and UE 101b is established. (2) Optionally, an RRC relay connection between UE 101a and UE 101b is established. Here, the expression "optionally" means that this step is optional and may not be performed in some embodiments. ● UE101a sends a "RRC Reconfiguration Message for Relay Sidelink" to UE101b, and the message is relayed by relay UE103. The "RRC Reconfiguration Message for Relay Sidelink" may also be named as "RRC Reconfiguration Message for Sidelink Relay", "RRC Reconfiguration Message for Sidelink Relay Connection", "RRC Reconfiguration Message for Relay Sidelink Connection", etc. ● UE101b sends a "RRC Reconfiguration Complete Message for Relay Sidelink" to UE101a, and the message is relayed by relay UE103. The "RRC Reconfiguration Complete Message for Relay Sidelink" may also be named as "RRC Reconfiguration Complete Message for Sidelink Relay", etc. (3) The following possible steps of relay UE103 may exist: ● Step (3a): Relay UE103 declares a sidelink RLF for the link between relay UE103 and UE101b when the following conditions occur: ≫ Trigger conditions for sending a failure notification with the failure cause of "sidelink RLF": a) In response to an indication from the sidelink RLC entity of relay UE103 that the maximum number of retransmissions for a specific destination (i.e., UE101b) has been reached, or b) In response to the expiration of timer T400, or c) In response to an indication from the sidelink MAC entity of relay UE103 that the maximum number of consecutive HARQ DTX for a specific destination has been reached, or d) In response to an integrity check failure indication from the sidelink PDCP entity of relay UE103. ● Step (3b): After relay UE103 sends an RRCReconfigurationSidelink message to UE101b, relay UE103 receives an RRCReconfigurationFailureSidelink message. ≫ Trigger conditions for sending a failure notification with the failure cause of "configuration failure": a) In response to receiving the RRC Reconfiguration Failure Sidelink message from UE101b. (4) When relay UE103 declares a sidelink RLF or when relay UE103 detects a configuration failure, relay UE103 sends a failure notification to UE101a. ● When an RLF of the link between relay UE103 and UE101b occurs or when relay UE103 receives an RRC reconfiguration failure message from UE101b, relay UE103 reports a failure notification to UE101a. ● The following information should be added to the failure notification: ≫ The destination ID associated with the link between UE101a and UE101b, or the destination ID associated with the link between relay UE103 and UE101b. ≫ Cause of failure: Sidelink RLF, or configuration failure. ≫ Optionally, the following additional information may be added to the failure notification: Maximum number of RLC retransmissions, T400 expiration, maximum number of consecutive HARQ DTXs, or integrity check failure. Here, the expression "optionally" means that these additional information are optional and may not be included in some embodiments. (5) UE101a receives a failure notification from relay UE103. The failure information may indicate "sidelink RLF" or "configuration failure". ● If the received failure notification indicates a sidelink RLF between relay UE103 and UE101b, UE101a may perform the following operations: ≫ UE101a declares a sidelink RLF of the link between UE101a and UE101b. ≫ UE101a declares a sidelink RLF of the link between UE101a and relay UE103. ≫ UE101a releases the DRB and SRB of the link between UE101a and UE101b. ≫ UE101a releases the DRB and SRB of the link between UE101a and relay UE103. ≫UE101a discards the configuration information of NR sidelink communication for the link between UE101a and UE101b. ≫UE101a discards the configuration information of NR sidelink communication for the link between UE101a and relay UE103. ≫UE101a resets the sidelink-specific MAC for the link between UE101a and UE101b. ≫UE101a resets the sidelink-specific MAC for the link between UE101a and relay UE103. ≫UE101a considers that the PC5 RRC connection for the link between UE101a and UE101b is released. ≫UE101a considers that the PC5 RRC connection for the link between UE101a and relay UE103 is released. ≫UE101a indicates the released state of the PC5 RRC connection (i.e., the PC5 RRC connection is unavailable) to the upper layer with respect to UE101b. (6) When UE101a receives a failure notification from relay UE103, UE101a may trigger to send a SidelinkUEinformation message to the serving BS of UE101a (e.g., BS102 as illustrated and exemplified in FIG. 1). On the other hand, UE101a is triggered to monitor the discovery resource pool for the relay reselection procedure. ● Regarding whether UE101a reports the failure information of the end-to-end relay connection to the BS: ≫UE101a receives failure information from relay UE103. The failure information includes the destination ID of UE101b, the cause of failure, and the ID of relay UE103. ≫A new cause of failure for this case may be the reception of sidelink RLF or the reception of configuration failure. ≫The failure information includes the true destination ID associated with multi-hop, e.g., the ID of UE101b. ≫After the BS receives the failure information, the BS may reconfigure UE101a to perform the relay reselection procedure.

[0063] Embodiment 2 Similar to Embodiment 1, according to Embodiment 2, a UE (e.g., UE101a as illustrated and exemplified in FIG. 1), a relay UE (e.g., relay UE103 as exemplified and illustrated in FIG. 1), and another UE (e.g., UE101b as illustrated and exemplified in FIG. 1) perform the following steps. Steps (1) and (2) of Embodiment 2 are the same as steps (1) and (2) of Embodiment 1. (1) A PC5 RRC connection of PC5 link 1 between UE101a and relay UE103 is established. Another PC5 RRC connection of PC5 link 2 between relay UE103 and UE101b is established. (2) Optionally, an RRC relay connection of the link between UE101a and UE101b is established. Here, the expression "optionally" means that this step is optional and may not be performed in some embodiments. (3) UE101a declares a side link RLF of the link between UE101a and relay UE103. Or, after UE101a sends an RRCReconfigurationSidelink message to relay UE103, UE101a receives an RRCReconfigurationFailureSidelink message from relay UE103. (4) UE101a is triggered to monitor a discovery resource pool for a relay reselection procedure.

[0064] FIG. 6 illustrates a flowchart of a method for reporting failure information according to some embodiments of the present application. This method may be performed by a UE (e.g., UE101a or UE101b as exemplified and illustrated in FIG. 1, UE(a) as exemplified and illustrated in FIG. 2, or UE as exemplified and illustrated in FIG. 3). Although described with respect to a UE, it should be understood that other devices may be configured to perform a method similar to that of FIG. 6.

[0065] In exemplary method 600 as illustrated in FIG. 6, an RRC relay connection of a link between a UE (e.g., UE101a illustrated and shown in FIG. 1) and another UE (e.g., UE101b illustrated and shown in FIG. 1) is established. In operation 601, the UE sends an "RRC reconfiguration message for relay side link" to a relay UE (e.g., relay UE103 illustrated and shown in FIG. 1).

[0066] In operation 602, the UE starts a timer for controlling the reconfiguration procedure. In operation 603, if the timer expires or the UE receives an RRC reconfiguration failure message for the relay side link from the relay UE, the UE reports failure information to the BS (e.g., BS102 illustrated and shown in FIG. 1). The failure information indicates a failure on the RRC relay connection of the link between the UE and the other UE described above.

[0067] The failure information in the embodiment of FIG. 6 is in a similar format or content as those of the failure information in the embodiment of FIG. 4. For example, similar to the embodiment of FIG. 4, in the embodiment of FIG. 6, the failure information may include the state of the link between the UE and the relay UE, and the state of the link between the relay UE and the other UE described above. Each of the states may represent "occurrence of RLF" or "link is available".

[0068] According to some embodiments, the UE receives an RRC reconfiguration message from the BS and performs a relay reselection procedure. The RRC reconfiguration message instructs the UE to perform a relay reselection procedure. According to some other embodiments, the UE autonomously performs a relay reselection procedure. For example, the UE autonomously performs a relay reselection procedure in response to reporting the failure information to the BS. The relay reselection procedure in the embodiment of FIG. 6 is the same as that in the embodiment of FIG. 4.

[0069] In one example, the failure information includes the ID of the other UE described above, which may also be named as the destination ID. For example, referring to FIG. 1, the failure information is ● If an end - to - end link is established between UE101a and UE101b, it includes the destination ID associated with the end - to - end link, or ● the destination ID associated with the link between relay UE103 and UE101b.

[0070] In one example, the fault information includes the cause of the fault. For example, the cause of the fault can be the side - link RLF of the RRC relay connection of the link between UE101a and UE101b. The cause of the fault can be a configuration fault of the RRC relay connection of the link between UE101a and UE101b.

[0071] In one embodiment, the UE declares the side - link RLF of the link between the UE and another UE as described above. For example, UE101a declares the side - link RLF of the link between UE101a and UE101b.

[0072] In a further embodiment, the UE further performs the following operations: ● Release the DRB and SRB of the link between the UE and another UE as described above, ● Discard the side - link communication configuration information of the link between the UE and another UE as described above, ● Reset the side - link specific MAC configuration information of the link between the UE and another UE as described above, ● Set the "connection state" of the link between the UE and another UE as described above to the "released state", and ● Indicate the "released state of the link between the UE and another UE as described above" to the upper layer of another UE as described above.

[0073] All the details described in all other embodiments of this application (for example, the details of how to handle a fault on the link between the relay UE and the UE) are applicable to the embodiment of FIG. 6. Moreover, the details described in the embodiment of FIG. 6 are applicable to all the embodiments of FIGS. 1 - 5, FIGS. 7 and 8.

[0074] FIG. 7 illustrates a flowchart of a method for transmitting an RRC reconfiguration failure message for a relay side link according to some embodiments of the present application. This method may be performed by a relay UE (e.g., the relay UE 103 illustrated and shown in FIG. 1). Although described with respect to a UE, it should be understood that other devices may be configured to perform in a manner similar to that of FIG. 7.

[0075] In an exemplary method 700 as illustrated in FIG. 7, at operation 701, a relay UE (e.g., the relay UE 103 illustrated and shown in FIG. 1) receives a "RRC reconfiguration message for relay side link" from a UE (e.g., the UE 101a illustrated and shown in FIG. 1). At operation 702, the relay UE starts a timer for controlling the reconfiguration procedure. At operation 703, if the relay UE receives an RRC reconfiguration failure side link message from another UE (e.g., the UE 101b illustrated and shown in FIG. 1), the relay UE transmits a "RRC reconfiguration failure message for relay side link" to the UE.

[0076] In one embodiment, the relay UE further transmits a "RRC reconfiguration message for relay side link" to the above-mentioned another UE. For example, the "RRC reconfiguration failure message for relay side link" includes the ID of the above-mentioned another UE, which may also be named as the destination ID. Referring to FIG. 1, the "RRC reconfiguration failure message for relay side link" may include a destination ID associated with the link between the relay UE 103 and the UE 101b, or a destination ID associated with the end-to-end link if the end-to-end link between the UE 101a and the UE 101b is established.

[0077] In one example, the "RRC reconfiguration failure message for relay side link" includes a cause of failure. Similar to the cause of failure in the failure notification of the embodiments of FIGS. 4-6, the cause of failure in the "RRC reconfiguration failure message for relay side link" includes side link RLF or configuration failure.

[0078] The details described in all other embodiments of this application (e.g., details of how to handle a failure on the link between the relay UE and the UE) are applicable to the embodiment of FIG. 7. Moreover, the details described in the embodiment of FIG. 7 are applicable to all embodiments of FIGS. 1-6 and FIG. 8.

[0079] The following text describes a specific embodiment 3 of the method as illustrated and exemplified in FIGS. 6 and 7.

[0080] Embodiment 3 According to Embodiment 3, a UE (e.g., UE101a as illustrated and exemplified in FIG. 1), a relay UE (e.g., relay UE103 as exemplified and illustrated in FIG. 1), and another UE (e.g., UE101b as illustrated and exemplified in FIG. 1) perform the following steps: (1) The PC5 RRC connection of PC5 link 1 between UE101a and relay UE103 is established. Another PC5 RRC connection of PC5 link 2 between relay UE103 and UE101b is established. (2) Optionally, UE101a sends an "RRC reconfiguration message for relay sidelink" to UE101b via relay UE103. Here, the expression "optionally" means that this step is optional and may not be performed in some embodiments. a) In case 1-1: i. When UE101a sends an "RRC reconfiguration message for relay sidelink", UE101a starts a timer. The timer is used to control the RRC reconfiguration procedure. ii. UE101a reports failure information to the network or BS (e.g., BS102 as exemplified and illustrated in FIG. 1) in response to the expiration of this timer. b) In case 1-2: i. After UE101a sends an "RRC reconfiguration message for relay sidelink" to UE101b, UE101a receives an "RRC reconfiguration failure message for relay sidelink". (3) UE101a may receive a "RRC Reconfiguration Failure Message for Relay Sidelink" from UE101b, and the message is relayed by the relay UE. Otherwise, a timer for controlling the RRC reconfiguration procedure may expire. (4) UE101a reports the failure information to the BS. a) The failure information may be included in the SidelinkUEInformation message. b) The failure information includes the destination ID (e.g., the ID of UE101b), the cause of the failure, and the ID of the relay UE103. i. New cause of failure for Case 1-1: Sidelink RLF of the relay connection. ii. New cause of failure for Case 1-2: Configuration failure of the relay connection. c) The state of the link between UE101a and the relay UE103 may also be included in the failure information and may be useful for the decision of the BS. d) The state of the link between the relay UE103 and UE101b may be included in the failure information. i. UE101a may report the failure information to the relay UE103. Whether the link between the relay UE103 and UE101b is available or not, the relay UE103 may respond to UE101a. e) The failure information includes the true destination associated with multi-hop, e.g., the ID of UE101b. f) After the BS receives the failure information from UE101a, the BS may reconfigure the UE to perform the relay reselection procedure.

[0081] FIG. 8 illustrates a simplified block diagram of an apparatus for a failure handling procedure according to some embodiments of the present application.

[0082] In some embodiments of the present application, the apparatus 800 may be a UE (e.g., UE101a or UE101b as illustrated and shown in FIG. 1, UE(a) as illustrated and shown in FIG. 2, or UE as illustrated and shown in FIG. 3), and may at least perform the method illustrated in FIG. 4 or FIG. 6.

[0083] In some other embodiments of the present application, the apparatus 800 may be a relay UE (e.g., relay UE 103 as illustrated and shown in FIG. 1 or UE (b) as illustrated and shown in FIG. 2), and may at least perform the methods illustrated in FIG. 5 or FIG. 7.

[0084] In some additional embodiments of the present application, the apparatus 800 may be a BS (e.g., BS 102 as illustrated and shown in FIG. 1 or BS as illustrated and shown in FIG. 3), and may at least perform some of the method steps as illustrated in any one of FIGS. 4 to 7.

[0085] As illustrated in FIG. 8, the apparatus 800 may include at least one receiver 802, at least one transmitter 804, at least one non-transitory computer-readable medium 806, and at least one processor 808 coupled to the at least one receiver 802, the at least one transmitter 804, and the at least one non-transitory computer-readable medium 806.

[0086] In FIG. 8, elements such as at least one receiver 802, at least one transmitter 804, at least one non-transitory computer-readable medium 806, and at least one processor 808 are described in the singular, but a plurality is contemplated unless a limitation to the singular is specified. In some embodiments of the present application, the at least one receiver 802 and the at least one transmitter 804 are coupled to a single device, such as a transceiver. In some embodiments of the present application, the apparatus 800 may further include an input device, a memory, and / or other components.

[0087] In some embodiments of the present application, the at least one non-transitory computer-readable medium 806 may store computer-executable instructions programmed to implement the operations of a method as described, for example, in view of any one of FIGS. 4 to 7, by the at least one receiver 802, the at least one transmitter 804, and the at least one processor 808.

[0088] One of ordinary skill in the art will appreciate that the operations of the methods described in connection with the aspects disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. The software modules may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of known storage medium. Additionally, in some aspects, the operations of the methods may reside as one or any combination or collection of code and / or instructions on a non-transitory computer-readable medium and may be incorporated into a computer program product.

[0089] While the present disclosure has been described in connection with its specific embodiments, it will be apparent to those of ordinary skill in the art that many alternatives, modifications, and variations are possible. For example, the various components of the embodiments may be exchanged, added, or substituted in other embodiments. Also, not all of the elements of each figure are necessary for the operation of the disclosed embodiments. For example, one of ordinary skill in the art will be enabled to make and use the teachings of the present disclosure by simply utilizing the elements of the independent claims. Accordingly, the embodiments of the present disclosure described herein are intended to be illustrative rather than limiting. Various changes may be made without departing from the spirit and scope of the present disclosure.

[0090] As used herein, the terms "comprising," "including," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Elements preceded by "a", "an", etc. do not, without further limitation, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises such element. Also, the term "another" is defined as at least a second or later. The terms "having," etc., as used herein, are defined as "including" as used herein.

Description of Symbols

[0091] 100 Wireless communication system 101a UE 101b UE 102 BS 103 Relay UE 800 Device 802 Receiver 804 Transmitter 806 Non-transitory computer-readable medium 808 Processor T400 Timer

Claims

1. A method performed by a first user equipment (UE), comprising: establishing a first PC5 radio resource control (RRC) connection for a link between the first UE and a relay UE, wherein a second PC5 RRC connection for a link between the relay UE and a second UE is established; receiving a failure notification from the relay UE, the failure notification indicating the occurrence of a failure on the link between the relay UE and the second UE; and a method comprising the steps of.

2. further comprising establishing an RRC relay connection for a link between the first UE and the second UE; The method according to claim 1, further comprising the steps of.

3. The failure notification is in response to establishing an RRC relay connection for a link between the first UE and the second UE, an identifier (ID) of the second UE associated with the RRC relay connection for the link between the first UE and the second UE; The method according to claim 1, comprising one of the IDs of the second UE associated with the link between the relay UE and the second UE.

4. The failure notification includes a cause of the failure, and the cause of the failure is one of a sidelink radio link failure (RLF) and a configuration failure; The method according to claim 1, comprising one of the steps of.

5. The failure notification is reaching the maximum number of retransmissions of the RLC entity of the relay UE; expiration of a timer for transmitting RRC reconfiguration for sidelink; reaching the maximum number of consecutive hybrid automatic repeat request (HARQ) discontinuous transmissions (DTX); The method according to claim 4, further comprising at least one cause of failure including a integrity check failure.

6. declaring a sidelink RLF for the link between the first UE and the relay UE, or declaring a sidelink RLF for the link between the first UE and the second UE in response to establishing an RRC relay connection for the link between the first UE and the second UE; The method according to claim 1, further comprising the steps of.

7. releasing a data radio bearer (DRB) and a signaling radio bearer (SRB) for the link between the first UE and the relay UE; discarding sidelink communication configuration information for the link between the first UE and the relay UE; In response to the establishment of an RRC relay connection of a link between the first UE and the second UE, releasing the DRB and SRB of the link between the first UE and the second UE; discarding the sidelink communication configuration information of the link between the first UE and the second UE The method according to claim 1, further comprising.

8. resetting the sidelink-specific media access control (MAC) configuration information of the link between the first UE and the relay UE; setting the connection state of the link between the first UE and the relay UE to a released state; indicating the released state of the link between the first UE and the relay UE to the upper layer of the second UE; In response to the establishment of an RRC relay connection of a link between the first UE and the second UE, resetting the sidelink-specific MAC configuration information of the link between the first UE and the second UE; setting the connection state of the link between the first UE and the second UE to a released state; indicating the released state of the link between the first UE and the second UE to the upper layer of the second UE The method according to claim 1, further comprising.

9. The fault notification is RRC signaling; a control packet data unit (PDU) in the sidelink adaptation protocol (SLAP) layer; The method according to claim 1, included in one of the MAC control elements (CE).

10. determining whether the first UE is within the coverage of a base station (BS); reporting fault information to the BS in response to a determination that the first UE is within the coverage of the BS and in response to receiving the fault notification, wherein the fault information is associated with the fault notification; The method according to claim 1, further comprising.

11. The fault information is the state of the link between the first UE and the relay UE; The method according to claim 10, including the state of the link between the relay UE and the second UE.

12. The state of the link between the first UE and the relay UE or the state of the link between the relay UE and the second UE is the occurrence of RLF The method according to claim 11, representing one of the availability of the link.

13. Receiving an RRC reconfiguration message from the BS, wherein the RRC reconfiguration message instructs the first UE to perform a relay reselection procedure; Performing the relay reselection procedure; The method according to claim 1, further comprising.

14. Performing a relay reselection procedure in response to receiving the failure notification; The method according to claim 1, further comprising.

15. The step of performing the relay reselection procedure includes: Monitoring a discovery resource pool to find one or more relay UEs; The method according to claim 13 or 14, further comprising selecting one relay UE from the one or more relay UEs.

16. Establishing a PC5 RRC connection of the link between the first UE and the selected one relay UE; The method according to claim 15, further comprising.

17. A method performed by a relay user equipment (UE), comprising: Detecting whether a failure has occurred on the link between the relay UE and a second UE, wherein a first PC5 radio resource control (RRC) connection of the link between the first UE and the relay UE is established, and a second PC5 RRC connection of the link between the relay UE and the second UE is established; In response to detecting that the failure has occurred on the link between the relay UE and the second UE, sending a failure notification to the first UE, wherein the failure notification indicates the occurrence of the failure on the link between the relay UE and the second UE.

18. The failure on the link between the relay UE and the second UE is: A sidelink radio link failure (RLF) of the link between the relay UE and the second UE; A failure during an RRC reconfiguration procedure between the relay UE and the second UE, and the failure notification is an RRC reconfiguration failure message for the relay sidelink. The method according to claim 17, which is one of the failures.

19. The failure notification is: In response to the establishment of the RRC relay connection of the link between the first UE and the second UE, the identifier (ID) of the second UE associated with the RRC relay connection of the link between the first UE and the second UE, and The method according to claim 17, comprising one of the ID of the second UE associated with the link between the relay UE and the second UE.

20. The fault notification includes a fault cause, and the fault cause is Side link RLF, and The method according to claim 17, comprising one of a configuration fault.

21. The fault notification is The maximum number of retransmissions of the radio link control (RLC) entity of the relay UE has been reached, and Expiration of a timer for transmitting RRC reconfiguration for side link, and The maximum number of consecutive hybrid automatic repeat request (HARQ) discontinuous transmissions (DTX) has been reached, and The method according to claim 20, further comprising at least one fault cause of a completeness check failure.

22. The fault notification is RRC signaling, and A control packet data unit (PDU) in the side link adaptation protocol (SLAP) layer, and The method according to claim 17, included in one of the MAC control elements (CE).

23. A method performed by a first user equipment (UE), comprising: Transmitting a radio resource control (RRC) reconfiguration message for a relay side link to a relay UE, wherein an RRC relay connection of a link between the first UE and a second UE is established; and Starting a timer for controlling the reconfiguration procedure; and Reporting fault information to a base station (BS) in response to expiration of the timer or in response to receiving an RRC reconfiguration failure message for a relay side link from the relay UE, wherein the fault information indicates a fault on the RRC relay connection of the link between the first UE and the second UE. A method comprising.

24. The fault information is The state of the link between the first UE and the relay UE, and The method according to claim 23, comprising the state of the link between the relay UE and the second UE.

25. The state of the link between the first UE and the relay UE or the state of the link between the relay UE and the second UE is The occurrence of a sidelink radio link failure (RLF) and The method according to claim 24, representing one of the link being available.

26. Receiving, from the BS, an RRC reconfiguration message that commands the first UE to perform a relay reselection procedure; Performing the relay reselection procedure; The method according to claim 23, further comprising:

27. Performing a relay reselection procedure; The method according to claim 23, further comprising:

28. The step of performing the relay reselection procedure includes: Monitoring a discovery resource pool to find one or more relay UEs; and Selecting one relay UE from the one or more relay UEs. The method according to claim 26 or 27.

29. Establishing a PC5 RRC connection for the link between the first UE and the one selected relay UE; The method according to claim 28, further comprising:

30. The failure information includes: An identifier (ID) of the second UE associated with the RRC relay connection of the link between the first UE and the second UE; or An ID of the second UE associated with the link between the relay UE and the second UE. The method according to claim 23.

31. The failure information includes a cause of the failure, and the cause of the failure includes: A sidelink RLF of the RRC relay connection; or A configuration failure of the RRC relay connection. The method according to claim 23.

32. Declaring a sidelink RLF of the link between the first UE and the second UE; The method according to claim 23, further comprising:

33. Releasing the DRB and SRB of the link between the first UE and the second UE; Discarding the sidelink communication configuration information of the link between the first UE and the second UE; Resetting the sidelink-specific MAC configuration information of the link between the first UE and the second UE; Setting the connection state of the link between the first UE and the second UE to a released state; and Indicating the released state of the link between the first UE and the second UE to the upper layer of the second UE. The method according to claim 23, further comprising at least one of:

34. A method performed by a relay user equipment (UE), comprising: receiving, by a first UE, a radio resource control (RRC) reconfiguration message for a relay sidelink; starting a timer for controlling a reconfiguration procedure; responding to receiving an RRC reconfiguration failure sidelink message from a second UE, and transmitting, to the first UE, an RRC reconfiguration failure message for the relay sidelink. **Claim 35** The method according to claim 34, further comprising transmitting, to the second UE, the RRC reconfiguration message for the relay sidelink. **Claim 36** **Claim 37** The RRC reconfiguration failure message for the relay sidelink includes an identifier (ID) of the second UE associated with an RRC relay connection of a link between the first UE and the second UE, or an ID of the second UE associated with a link between the relay UE and the second UE. **Claim 38** The RRC reconfiguration failure message for the relay sidelink includes a cause of failure, and the cause of failure includes one of a sidelink radio link failure (RLF) and a configuration failure. **Claim 39** **Claim 40** At least one non-transitory computer-readable medium storing computer-executable instructions, at least one receiving network, at least one transmitting network, at least one processor coupled to the at least one non-transitory computer-readable medium, the at least one receiving network, and the at least one transmitting network, wherein the computer-executable instructions cause the at least one processor to implement the method according to any one of claims 1 to 16. An apparatus. **Claim 41** At least one non-transitory computer-readable medium storing computer-executable instructions, at least one receiving network, at least one transmitting network, at least one processor coupled to the at least one non-transitory computer-readable medium, the at least one receiving network, and the at least one transmitting network, wherein the computer-executable instructions cause the at least one processor to implement the method according to any one of claims 17 to 22. An apparatus. **Claim 42** At least one non-transitory computer-readable medium storing computer-executable instructions, At least one receiving network, At least one transmitting network, At least one processor coupled to the at least one non-transitory computer-readable medium, the at least one receiving network, and the at least one transmitting network, The computer-executable instructions cause the at least one processor to implement the method according to any one of claims 23 to 33, An apparatus. **Claim 41** At least one non-transitory computer-readable medium storing computer-executable instructions, At least one receiving network, At least one transmitting network, At least one processor coupled to the at least one non-transitory computer-readable medium, the at least one receiving network, and the at least one transmitting network, The computer-executable instructions cause the at least one processor to implement the method according to any one of claims 34 to 37, An apparatus.

Images